As is known in the art, a field seed planter includes a group of seed chutes or seed discharge tubes, one for each row for simultaneous planting. Each of these seed chutes or tubes convey individual seeds from a seed dispenser in conjunction with a hopper or other seed supply to individual furrows formed in the ground by the planter as it moves across a field. Various monitoring and counting arrangements have been utilized for obtaining a count of the number of seeds dispensed by such seed planters. Such counting is particularly useful in determining and controlling the density or population of seeds planted in order to optimize crop yield. Also, more recently, seed spacing information is of interest since yield is positively affected by the uniform spacing of such seeds.
The prior art has generally utilized photoelectric devices to sense the passage of individual seeds through the seed chutes or tubes. Such arrangements generally have included a light source such as a light emitting diode (LED) positioned to one side of the seed chute or tube and a light responsive element such as a photoresponsive transistor or diode positioned at the opposite side of the tube. Hence, the photoresponsive element normally produces a steady state signal level in response to the light incident thereupon from the light source. However, as a seed passes through the chute and comes between the light source and light responsive element, the level of light incident upon the light responsive element momentarily decreases. Responsively, the light responsive element produces a momentary change in the normal or steady state signal level output, which represents potentially a seed.
Various electrical and electronic circuits have been devised to receive the light responsive element output signal and respond to the changes in the level thereof due to the passage of a seed through the seed chute. Ideally, such electronic circuits should produce a discrete signal or pulse for each seed passing through the chute. Accordingly, accurate information as to the number of seeds dispensed by a given chute may be obtained by counting these pulses.
However, various challenges to accuracy of seed counting are encountered including considerable dirt, dust and the like as the planter moves through the field. Moreover, various coatings are commonly provided on seed grains, and these coatings often accumulate in the seed chutes or tubes. Accordingly, the foregoing accumulations of material in the seed tube tend to interfere with proper operation of the photoresponsive system. Additionally, the characteristics of the photoresponsive element and light source change somewhat over time, thus changing both the ambient light level incident upon the photoresponsive element and its response thereto and to changes in light level due to the passage of seeds. These changes may, if uncompensated for, greatly reduce the reliability of the response of the photoresponsive element. A related problem is that of drift or changes over time in the nominal characteristics of the circuit elements utilized in the electronic circuits. For example, various circuit parameters such as gain, voltage levels, or the like may vary or drift somewhat over time. Such drift may occur for example due to environmental changes, detracting from optimum operation of the circuits and hence from the reliability of the count obtained therefrom.
Yet another challenge occurs as seed deposition rates increase the ability to reliably count multiple seeds which fall through the seed chute in close proximity or even partially overlapping decrease. In such instances, both the photoresponsive element and the associated electronic circuit may be unable to respond rapidly enough to reliably produce a separate counting pulse for each seed. A related problem is often encountered with relatively small, fast moving seeds such as soybeans. Additionally, soybeans are generally dispensed at a relatively high rate or density. Hence, today's seed sensing systems may be incapable of sufficiently rapid response to reliably count each seed and to distinguish between seeds and dust or other foreign matter.